Comparing Soil Water Dynamics in Organic and Conventional Tea Fields Using Numerical Modeling and Non-linear Information Theory

Organic agriculture has gained increasing recognition in recent years for its benefits to natural ecosystems and humanity, particularly its influence on water resource utilization and environmental conservation. Tea, a key economic crop in Pinglin, Taiwan, depends heavily on precipitation and soil moisture for its growth. However, recent drought conditions in Taiwan have significantly challenged tea cultivation and production. Therefore, understanding how different agricultural management practices affect the vadose zone water balance is essential for improving the resilience of tea fields to drought.

Soil moisture in organic tea fields decreases more rapidly than in conventional ones after heavy rainfall. In this study, we utilized long-term in situ observations from two neighboring tea fields in Pinglin—one under conventional management and the other organic-certified—along with data on hydraulic and climatic variables (e.g., rainfall, soil water content, evapotranspiration, and soil temperature). Using these in situ data and collected soil samples, we analyzed and compared the hydraulic properties of the two fields. The HYDRUS-1D model was applied to simulate water dynamics, enabling us to characterize infiltration and surface runoff and compare the impacts of different farming practices on tea field hydrology. Additionally, we employed the Convergent Cross Mapping (CCM) method to investigate the nonlinear dynamical system (NDS) relationships among water balance variables in the tea fields (e.g., rainfall, evapotranspiration, soil water content). This approach allowed us to understand the causal relationships between soil moisture and other variables and to identify the time lag between environmental conditions and the onset of drought.

In Pinglin, most tea fields depend on rain-fed irrigation. Findings from this research can support the development of irrigation plans to enhance drought resilience in tea production and offer more comprehensive recommendations for sustainable agricultural practices.